Production of naphthenic acids



Nov. 19, 1942. KELLOG ETAL 2,30i,285

PRODUCTION OF NAPHTHENIG ACIDS I Filed Feb. 18, 1941 Patented Nov. 10, 1942 Henry B. Kellog, Union City, and Peter J. Gaylor,

Union, N. J., assignorsto Standard Oil Development Company, a corporation of Delaware Application February 18, 1941, Serial No. 379,486

- 7 Claims.

The present invention is concerned with the production of high quality naphthenic acids. The invention more particularly relates to the purification of naphthenic acids, especially those naphthenic acids which are segregated from pe- 5 troleum oils in various refining operations. In accordance with our process, an efiicient and economical method is provided for effecting the removal of objectionable impurities from 'naphthenic acids which heretofore have been rela- 0 tively difiicult to remove completely, and which have rendered naphthenic acids, particularlythose'secured from petroleum oil sources, unsuitable for'many uses.

It is Well-known in the art that petroleum oils contain naphthenic acids, which substances are segregated from the petroleum oil by various methods as, for example, from the spent caustic solutions secured during the refining of these oils.

The naphthenic acids generally comprise a mixture of acidic compounds having rather complex molecular structures and containing principally carbon, hydrogen and oxygen. The molecular weights of the respective acids vary considerably. Various naphthenic acids found in petroleum are low boiling liquids while others are heavy, viscous liquids at ordinary temperatures and pressures. In general, these acids are characterized by containing at least one carboxyl group attached to the naphthenic hydrocarbon molecule. Various methods have been introduced to segregate and to purify naphthenic acids recovered from petroleum oils. For example, naphthenic acid crude fractions have been distilled under vacuum in order to segregate particularly desirable fractions. It has also been suggested that the crude naphthenic acid fractions or selected fractions be contacted with various oxides, such as manganese dioxide,

chromic oxide, ferric oxide, cupric oxide, and related oxides and compounds. -However, when employing these operations, it has been extremely diflicult to decolorize satisfactorily the naphthenic acid constituents and especially difllcult to remove the last traces of impurities which impart a disagreeable odor to the refined naphthenic acid products. I

We have, however, now discovered a particularly desirable method by which naphthenic acids may be readily and efiiciently deodorized and decolorized. Our process comprises contacting the crude naphthenic acids or fractions thereof with an activated copper chromite catalyst, known as Adkins catalyst and prepared as disclosed in Adkins book, "Reactions of Hydrogen, University of Wisconsin Press, 1937, pages 13 and 14. Our naphthenic acids are generally obtained from a naphthenic acid-bearing petroleum oil by washing the oil with an alkali solution'such as sodium hydroxide. The process of our invention may be readily understood by reference to the attached drawing illustrating an embodiment of the same.

A feed oil, which for the purposes of illustration is taken to be an uncracked petroleum oil fraction segregated from a naphthenic crude and boiling inthe gas oil boiling range, is introduced into contacting zone I by means of' feed line 2.

' In contacting zone l the feed oil is scrubbed with an aqueous alkali metal hydroxide solution which is introduced into zone I by means of feed line 3. .For purposes of description it is assumed that the aqueous alkali metal hydroxide solution comprises a dilute sodium hydroxide solution. It is to be understood that zone I may comprise any suitable number and arrangement of units. The treated feed oil is Withdrawn from zone I by means of.line 4 and handled in any manner desirable. The spent sodium hydroxide solution is withdrawn from zone I by means of line 5 and passed to zone 6 in which temperature and pressure conditions are adjusted to remove water .overhead by means of line I.

The concentrated sodium naphthenate solution is withdrawn from zone 6 by means of line 8 and passed into acidification zone 9 equipped with a'stirrer in' which theconcentrated salt solution is acidified with a suitable acid introduced by means of line I 0. For purposes of description, it is assumed that the acid comprises concentrated sulfuric acid. The acidified product is Withdrawn from acidification zone 9 by means of line II and passed into distillation zone I2 in which temperature and pressure conditions are adjusted to remove the naphthenic acids and some water overhead by means of line I3. Non-volatile reaction products and other non-naphthenic acid constituents are removed as a bottoms from distillation zone I2 by means of line I 4. The overhead naphthenic acid constituents are condensed in cooler I5, passed to a separator 28 wherein water is separated-from the acids and drawn 011 at 25. The separated acids are then drawn ofi at line 30 and passed to distillation zone IS. A relatively small quantity of low boiling distillate is removed under vacuum through line H, while a small quantity of relatively high boiling bottoms is removed by means of I 8. A relatively large quantity of the desired intermediate boiling constituents or a so-called "heart 'cut is removed by means of line III. This intermediate bofling fraction is condensed in cooler 20 and passed to distillation zone 2| wherein it is distilled under vacuum in'the presence of a copper-barium chromite catalyst, known asthe "Adkins catalyst, prepared as hereinafter described. This catalyst is introduced preferably in suspension in oil or naphthenic acid from line I9, into zone 2| by means of line II. Temperature and pressure conditions are'adjusted to remove overhead by means of line 23 the purified naphthenic acids which are substantially colorless and freed of the obnoxious odor usually associated with such acids. I This overhead product is condensed in cooler 24, withdrawn from the system by means of line 25 and further refined or handled in any manner desirable. The impurities comprising color-forming and odor-imparting substances, together with spent catalyst, are withdrawn from distillation zone 2| by means of line 26. It is to be understood that the various zones 6, 9, l2, l6, and 2| may comprise any suitable number and arrangement of units, and that the respective operations may b either adapted to a batch or to a continuous operation. Under certain conditions it may be desirable to distill the entire fraction removed overhead from zone I! rather than a heart cut. If this operation be utilized, the overhead from zone I2 is introduced directly into distillation zone 2| by means of line 21.

It is also possible to contact naphthenic acid vapors directly with the catalyst in the form of a bed in a treating tower, rather than by contacting the liquid acids during distillation. Hydrogen or other treating gases may be present during the treatment, and the catalyst may be in powder form, or it may be formed or extruded into pellets, ribbons, etc., either with or without carriers such as clays, alumina, silica gel, etc., or mixtures thereof.

The process of the present invention may be widely varied. It may be adapted for decoloriz- .ing and deodorizing naphthenic acids secured from any source. It is, however, particularly adapted for the refining of naphthenic acids secured from a petroleum oil source, in order to produce a product of enhanced odor and color. The invention is particularly adapted for the refining of naphthenic acids secured from uncracked petroleum oil fractions boiling in the gas oil and reduced'crude ranges, which have been segregated from naphthenic crudes. In general, these petroleum oil fractions boil in the general range from about 400 F. to 900.F. or in the range from. about 400 F. to 700 F.

The crude naphthenic acids may be segregated from the petroleum oils utilizingany suitable medium. It is, however, preferred to contact the petroleum oils with an alkaline solution such as that now used in the art.

Although thetotal naphthenic acids may be distilled in the presence of the catalyst of 'the present invention, it is preferred to segregate a heart cut and to treat this cut as described. This heart out, in general, comprises the fraction consisting of 5% to 95% or even to 90% out of the crude naphthenic acids.

The catalyst used for decolorizing naphthenic acid according to the present invention is commonly known as Adkins' catalyst and is prepared by the following procedure:

900 ml. of a solution (at 80 C.) containing 260 g. of trihydrated' copper nitrate and 31 g.yof barium nitrate are added to 900 ml. of a solution (at 25 C.) containing 151 g. of ammonium dichromate and 225 ml. of 28 per cent ammonium hydroxide. The precipitate is filtered, the cake pressed with a spatula, and sucked as dry as possible'. The product is dried in an oven at 75 C. to 80 C. for twelve hours and then pulverized. It is decomposed in three portions in a casserole over a free flame. position, the powder is continuously stirred with a spatula and the heating so regulated that the In carrying out the decomevolution of gases does not become violent. This is accomplished by heating only one side of the I casserole and stirring the powder more rapidly when the decomposition starts to spread throughout the mass. During this process the color of the powder changes from orange to brown and finally to black. When the entire mass has become black, the evolution of gases ceases, and the powder is removed from the casserole and allowed to cool. The combined product is then leached for thirty minutes with 600 ml. of 10% acetic acid solution, filtered, and washed with 600 ml. of water in six portions, dried for 12 hours at C., and pulverized. The yield of catalyst is g. (Copper sulfate "and sodium dichromate may be substituted for the corresponding nitrate and potassium salts.)

The catalyst comprising a copper-barium chromite known as the Adkins catalyst," prepared as described in the above identified publication, may be employed in any particle size.

The amount of catalyst employed may varywidely naphthenic acids and the concentration of thedepending upon lthe particular type of impurities present. The amount of copperbarium utilization is generally less than 10%,

preferably less than 5%,}.based upon the weight of the naphthenic acids being treated. Particularly desirable results have been secured when the amount of catalyst employed in the distillation operation is in the range from about 0.25% to 1%.

In order to illustrate following examples are given,

the invention further, the 'which should not be construed as limiting the invention in any manner whatsoever.

Example 1 A naphthenic acid crude fraction was prepared in the following manner:

A cracked petroleum oil which was segregated from a naphthenic crude was contacted with a dilute sodium hydroxide solution. The spent alkaliwas separated and water removed therefrom. The concentrated salt solution thus prepared was then contacted with concentrated sulfuric acid in order to generate the naphthenic acids from the sodium naphthenates. The acidified solution was then distilled in order to segregate the crude naphthenic acids.

The latter were then distilled under vacuum and a 10% to 88% heart out segregated, utilizing a temperature of from 125 C. to 200 C., at 5 mm. pressure.

This cut was thezitreated with various metal compounds and the Robinson color of the final From the above, it is apparent that neither cupric oxide nor chromium oxide nor combinations of the two oxides give anywhere near the improvement in color as that obtained with an equivalent weightof Adkins catalyst prepared as described above.

Example 2 'A crud naphthenic acid fraction prepared as described in Example 1 was treated with the catalyst of the present invention, except that the entire crude fraction was treated rather than a heart out of the same. The distillation in the presence of the Adkins catalyst was conducted at a temperature in the range from about 125 C. to about 180 C., at a pressure of 30 mm. The results were as follows:

Robinson color Original (dark reddish brown) (no match) Original+0.5% Adkins catalyst- 18.75

Upon straight distillation the same fraction has a Robinson color of about 12, showing that the Adkins catalyst gives a decided improvement in color. The odor of the acids was likewise greatly improved.

It is to be understood that the product produced in accordance with the present invention may be handled in any manner desirable. Anti-- oxidants may be added in order to stabilize the treated naphthenic acids, such as by'the addi-- tion of 0.001 to 0.1% of tertiary amyl phenol or similar materials.

What we claim as new and wish to protect by Letters Patent is:

1. Process for decolorizing impure naphthenic acids which comprises contacting said naphthenic acids in the presence of an activated copper barium chromite.

2. Process as defined by claim 1, in which said contacting operation is carried out at a'tempera ture range fromabout 100 C. to 200 C.

3. Improved process for the purification of naphthenic acids recovered .from petroleum oils containing the same, which comprises segregating naphthenic acids from said petroleum oils comprising distilling said naphthenic acids in the presence of a copper-barium chromite catalyst. 4. Process as defined by claim 3, in which said petroleum oil comprises an uncracked petroleum oil boiling in the gas oil boiling range, said petroleum oil being secured from a naphthenic crude.

5. Process as defined by claim 3, in which a heart out of the naphthenic acids is distilled under vacuum in the presence of the catalyst.

6. Process for improving odor and color of crude naphthenic acid fractions, which comprises distilling said crude naphthenic acid fractions in' order to segregate an intermediate boiling out, then distilling said intermediate boiling cut in the presence of a copper-barium chromite, whereby naphthenic acids of greatly enhanced odor and color are removed overhead.

7. Process as defined by claim 6, in which said intermediate boiling cut is about the 10% to 90% fraction. v

HENRY B. KELLOG. PETER J. GAYLOR. 

